But the diversity concept is really quite different. Its premise is that where there are, for example, only white people in a discussion, then the viewpoints, as seen through the eyes of persons of a different racial or ethnic background--meaning those aspects of difference or sameness from a person who has experienced life as a black person or as a Latino or as a disabled person, no matter how varied from black person to black person or Latino to Latino, will in fact be missing. This is true without regard to the diversity on other, non-racial or ethnic grounds, of the group. University officials seeking to create a rigorous intellectual environment as well as prepare students for leadership in a multi-racial world, determined that the one-race dimension that so many students get in their segregated elementary and secondary classrooms did not serve this purpose. Admissions programs to promote diversity recognize the salience of race and ethnicity without making any assumptions about the cohesiveness or sameness of viewpoint among members of any group. In fact, the more varied the viewpoint of those persons typically absent from the conversation, the better, which is why a critical mass of minority students is needed--to prevent the stereotyping that would be likely to occur if there were only a token number of minorities at the school.
This is all well and good, but what gives Howard the standing to make this case? Howard University's student body is 86% African American. Less than 5% of their campus is white or Asian. Is Howard thus implicitly saying diversity is valuable for schools where the majority of students are white, but has no value to majority-black schools? This is a particularly hypocritical argument coming from Howard, which as a private university could impose racial quotas without regard to the constitutional issues Michigan faces. Howard also receives special funds from the federal government as a "historically black college," meaning they actually benefit from practicing a mild form of racial segregation.
Now, this is not to suggest Howard should start altering admissions criteria to admit more white people. Such an argument would be absurd on its face—"a critical mass of white students is necessary to prevent stereotyping." But this only further erodes the Michigan supporters argument.
When you judge people as members of a racial collective, as the Michigan policy does, you send the message that they must tie their personal identity to said race. Once you de-individualize people that way, regardless of their race, then of course they're going to argue they need a "critical mass" to express themselves. After all, mobs only have power when they act in numbers.